U.S. patent number 8,691,016 [Application Number 13/522,007] was granted by the patent office on 2014-04-08 for deposition apparatus, and deposition method.
This patent grant is currently assigned to Sharp Kabushiki Kaisha. The grantee listed for this patent is Nobuhiro Hayashi, Shinichi Kawato, Tohru Sonoda. Invention is credited to Nobuhiro Hayashi, Shinichi Kawato, Tohru Sonoda.
United States Patent |
8,691,016 |
Sonoda , et al. |
April 8, 2014 |
Deposition apparatus, and deposition method
Abstract
A deposition mask 601 is used to form a thin film 3 in a
prescribed pattern on a substrate 10 by deposition. Each of a
plurality of improved openings 62A of the deposition mask 601 has a
protruding opening portion 64, and is formed so that the opening
amount at an end in a lateral direction is larger than that in a
central portion in the lateral direction. In a deposition apparatus
50, the deposition mask 601 is held in a fixed relative positional
relation with a deposition source 53 by a mask unit 55. In the case
of forming the thin film 3 in a stripe pattern on the substrate 10
by the deposition apparatus 50, deposition particles are
sequentially deposited on the substrate 10 while relatively moving
the substrate 10 along a scanning direction with a gap H being
provided between the substrate 10 and the deposition mask 601.
Inventors: |
Sonoda; Tohru (Osaka,
JP), Hayashi; Nobuhiro (Osaka, JP), Kawato;
Shinichi (Osaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Sonoda; Tohru
Hayashi; Nobuhiro
Kawato; Shinichi |
Osaka
Osaka
Osaka |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
Sharp Kabushiki Kaisha (Osaka,
JP)
|
Family
ID: |
44355059 |
Appl.
No.: |
13/522,007 |
Filed: |
October 29, 2010 |
PCT
Filed: |
October 29, 2010 |
PCT No.: |
PCT/JP2010/006414 |
371(c)(1),(2),(4) Date: |
July 12, 2012 |
PCT
Pub. No.: |
WO2011/096030 |
PCT
Pub. Date: |
August 11, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120295379 A1 |
Nov 22, 2012 |
|
Foreign Application Priority Data
|
|
|
|
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Feb 3, 2010 [JP] |
|
|
2010-022104 |
|
Current U.S.
Class: |
118/720; 438/34;
438/30; 438/944; 118/504; 118/726; 438/758; 427/248.1;
427/255.6 |
Current CPC
Class: |
H01L
51/0011 (20130101); C23C 14/12 (20130101); H01L
51/001 (20130101); C23C 14/042 (20130101); H01L
27/3211 (20130101); H01L 51/56 (20130101) |
Current International
Class: |
B05C
11/11 (20060101); C23C 16/00 (20060101); H01L
21/469 (20060101); H01L 21/31 (20060101); H01L
21/00 (20060101) |
Field of
Search: |
;438/34,758,778,780
;118/504,726,301 ;427/248.1,255.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
10-102237 |
|
Apr 1998 |
|
JP |
|
2000-48954 |
|
Feb 2000 |
|
JP |
|
2007-5123 |
|
Jan 2007 |
|
JP |
|
2007-005123 |
|
Jan 2007 |
|
JP |
|
2007-191753 |
|
Aug 2007 |
|
JP |
|
2007-227359 |
|
Sep 2007 |
|
JP |
|
2007-265707 |
|
Oct 2007 |
|
JP |
|
Other References
International Search Report received for PCT Patent Application No.
PCT/JP2010/006414, mailed on Nov. 22, 2010, 5 pages (2 page of
English translation and 3 pages of PCT Search Report). cited by
applicant .
Japanese Patent Application No. 2009-213570, filed on Sep. 15,
2009, titled "Jouchakusouchi oyobi Jouchakuhouhou", pp. 2-61, in 30
pages. cited by applicant.
|
Primary Examiner: Wilczewski; Mary
Assistant Examiner: Peterson; Erik T
Attorney, Agent or Firm: Morrison & Foerster LLP
Claims
The invention claimed is:
1. A deposition apparatus, comprising: a deposition mask that is
used to form a thin film in a stripe pattern on a substrate by
deposition, including a plate-like mask body, a and a plurality of
openings arranged in line in the mask body, the plurality of
openings including an improved opening in which an opening amount
in a longitudinal direction perpendicular to a lateral direction
varies depending on a position in the lateral direction, and the
lateral direction is a direction parallel to a direction in which
the plurality of openings are arranged, and the improved opening
being formed so that the opening amount at an end in the lateral
direction is larger than that in a central portion in the lateral
direction; a deposition source that emits deposition particles
forming the thin film; a mask unit that includes the deposition
mask and the deposition source, and maintains a fixed relative
positional relation between the deposition mask and the deposition
source; a substrate support apparatus that supports the substrate;
and a moving apparatus that relatively moves at least one of the
mask unit and the substrate along a predetermined scanning
direction with a constant gap being provided between the substrate
and the deposition mask, wherein the deposition mask is placed so
that the longitudinal direction is parallel to the scanning
direction, and a distance of the constant gap is in a range of 50
.mu.m to 1 mm.
2. The deposition apparatus of claim 1, wherein the improved
opening has a protruding opening portion in at least one end
portion in the longitudinal direction, and the protruding opening
portion opens in the end in the lateral direction so as to protrude
with respect to the central portion in the lateral direction.
3. The deposition apparatus of claim 2, wherein the protruding
opening portion is formed so that its opening amount gradually
increases as a distance from the central portion in the lateral
direction toward the end in the lateral direction increases.
4. The deposition apparatus of claim 3, wherein the protruding
opening portion is divided into a plurality of partial opening
portions.
5. A deposition method for forming the thin film in a stripe
pattern on the substrate by using the deposition apparatus of claim
1, comprising: an aligning step of, with the substrate being
supported by the substrate support apparatus and with the gap being
provided between the substrate and the deposition mask, aligning
the mask unit and the substrate so that the mask unit faces the
substrate; and a deposition step of forming the thin film by
sequentially depositing the deposition particles while relatively
moving at least one of the mask unit and the substrate along the
predetermined scanning direction by the moving apparatus.
6. The deposition method of claim 5, wherein a substrate for an
organic EL display in which a plurality of pixels each having a
light-emitting region configured to emit light are arranged in a
grid pattern is used as the substrate, the plurality of openings
are placed so as to face a plurality of film formation pixels that
are included in the plurality of pixels, and the deposition mask is
positioned so that each of the light-emitting regions of the film
formation pixels is located inside the improved opening in the
lateral direction with a gap therebetween, as viewed from a
direction perpendicular to the substrate.
7. The deposition method of claim 5, wherein a first relational
expression (Lw/L.gtoreq.T/Tw) is satisfied, where a centerline
passes through a center in the lateral direction of the improved
opening and extends in the longitudinal direction, "Lw" represents
the opening amount of the improved opening including the protruding
opening portion, at a predetermined distance W from the centerline
toward the end in the lateral direction, and if the improved
opening has no protruding opening portion, "Tw" represents a
thickness of the thin film at the predetermined distance, "L"
represents the opening amount in the central portion in the lateral
direction, and "T" represents a thickness in the central portion in
the lateral direction of the thin film (a unit of "T," "L," "Tw,"
and "Lw" is millimeter).
8. A deposition apparatus that is used to form a thin film in a
stripe pattern on a substrate by deposition, comprising: a
deposition mask having a plurality of openings arranged in line; a
deposition source that emits deposition particles forming the thin
film toward the substrate; a mask unit that includes the deposition
mask and the deposition source, and maintains a fixed relative
positional relation between the deposition mask and the deposition
source; a substrate support apparatus that supports the substrate;
and a moving apparatus that relatively moves at least one of the
mask unit and the substrate along a predetermined scanning
direction with a constant gap H being provided between the
substrate and the deposition mask, wherein the deposition mask is
placed so that a lateral direction in which the plurality of
openings are arranged is perpendicular to the scanning direction,
the plurality of openings include a second improved opening that is
formed by a plurality of element openings separated from each other
in the lateral direction, the plurality of element openings in the
second improved opening adjoin each other with a constant gap S
therebetween in the lateral direction, a distance of the constant
gap H is in a range of 50 .mu.m to 1 mm, a second relational
expression (S<H.times.tan .theta., .theta.=.alpha. when
.alpha..ltoreq..beta., and .theta.=.beta. when .alpha.>.beta.)
is satisfied, where ".alpha." represents a spread angle at which
the deposition particles spread with respect to an emission
direction substantially perpendicular to the substrate, and
".beta." represents a largest angle at which the deposition
particles can pass through the element opening (a unit of "S" and
"H" is micrometer, and a unit of ".alpha." and ".beta." is degree),
as viewed from the scanning direction, and adjoining ends of films
formed by the deposition particles passing through the plurality of
element openings and adhering to the substrate integrally overlap
each other to form the thin film.
9. A deposition method for forming the thin film in a stripe
pattern on the substrate by using the deposition apparatus of claim
8, comprising: an aligning step of, with the substrate being
supported by the substrate support apparatus and with the gap being
provided between the substrate and the deposition mask, aligning
the mask unit and the substrate so that the mask unit faces the
substrate; and a deposition step of forming the thin film by
sequentially depositing the deposition particles while relatively
moving at least one of the mask unit and the substrate along the
scanning direction by the moving apparatus.
10. The deposition method of claim 9, wherein a substrate for an
organic EL display in which a plurality of pixels each having a
light-emitting region configured to emit light are arranged in a
grid pattern is used as the substrate, the plurality of openings
are placed so as to face a plurality of film formation pixels that
are included in the plurality of pixels, and the deposition mask is
positioned so that each of the light-emitting regions of the film
formation pixels is located inside the second improved opening in
the lateral direction with a gap therebetween, as viewed from a
direction perpendicular to the substrate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This is a U.S. National Phase patent application of
PCT/JP2010/006414, filed Oct. 29, 2010, which claims priority to
Japanese Patent Application No. 2010-022104, filed Feb. 3, 2010,
each of which is hereby incorporated by reference in the present
disclosure in its entirety.
TECHNICAL FIELD
The present invention relates to deposition masks that are
preferably used in, e.g., large-sized organic EL (Electro
Luminescence) displays etc.
BACKGROUND ART
In recent years, a larger size, higher image quality, and lower
power consumption have been required for flat panel displays, and
high image quality organic EL displays capable of being driven at a
low voltage have received considerable attention. The organic EL
displays have the following structure. For example, in full color
active matrix organic EL devices, thin film-like organic EL
elements are provided on a substrate having thin film transistors
(TFTs) thereon. In the organic EL element, organic EL layers
including red (R), green (G), and blue (B) light-emitting layers
are stacked between a pair of electrodes, and each light-emitting
layer emits light in response to a voltage applied between the
electrodes. This light is used to display an image.
In manufacture of such organic EL displays, thin films such as
light-emitting layers and electrodes are patterned by using a
technique such as a vacuum deposition method, an ink jet method, or
a laser transfer method. For example, in low molecular organic EL
displays (organic light-emitting diodes (OLED)), the vacuum
deposition method is mainly used to pattern the light-emitting
layers.
In the vacuum deposition method, a mask having a predetermined
opening patterned therethrough is fixed to a substrate in close
contact therewith, and is placed in a vacuum chamber so that the
mask side of the substrate faces a deposition source. Then, a
film-forming material is deposited from the deposition source to a
desired position on the substrate through the opening of the mask.
A thin film such as the light-emitting layers is patterned in this
manner. The light-emitting layer of each color is separately
deposited color by color (separate deposition). In particular, a
mass production process uses a mask (a full contact shadow mask)
having the same size as the substrate, and the substrate having the
mask in close contact therewith is typically fixed at a
predetermined position with respect to the deposition source when
performing deposition.
A vacuum deposition method is also known, in which deposition is
performed while relatively moving a substrate etc. with respect to
a deposition source (Patent Document 1). In Patent Document 1, a
mask is used in which a plurality of small holes or long slit holes
having a smaller area than an electrode to be formed are formed at
predetermined intervals. Deposition is performed while moving the
mask in a direction crossing the direction in which the small holes
etc. are arranged, whereby the electrode having a predetermined
pattern is formed.
Regarding the present invention, a method is disclosed in which
unevenness of the surface of a thin film, which is produced by a
deposition process, is reduced by using predetermined conditions
such as the emission angle of a thin film material that is emitted
from a deposition source, positioning of a substrate and a
deposition mask, etc. (Patent Document 2).
In Patent Document 2, a mask having mesh patterns with different
aperture ratios for the pixels of each color (RGB) is used in order
to form a hole transport layer having different thicknesses for the
pixels of each color by a deposition method. This mask is placed to
face the substrate with a spacer interposed therebetween, and is
mounted in a predetermined deposition apparatus. When emitted from
the deposition source toward the substrate, the thin film material
(the material of the hole transport layer) is deposited on the
substrate according to the aperture ratios, thereby forming a hole
transport layer having different thicknesses. The hole transport
layer thus formed is heated and melted, and then solidified in
order to make its surface flat.
A method of using predetermined conditions such as the emission
angle of the thin film material emitted from the deposition source,
etc. is disclosed as a method of eliminating this heat treatment.
Specifically, the deposition conditions are determined so as to
satisfy the relation of tan(90-.theta./2)=H/W, where ".theta."
represents the emission angle of the thin film material from the
deposition source, "H" represents the interval between the
substrate and the mask, and "W" represents the mesh width of the
mask. This allows the thin film material emitted from the
deposition source to be deposited on the substrate below the mesh
patterns, whereby the unevenness of the thin film surface is
reduced.
CITATION LIST
Patent Document
PATENT DOCUMENT 1: Japanese Patent Publication No. H10-102237
PATENT DOCUMENT 2: Japanese Patent Publication No. 2007-5123
SUMMARY OF THE INVENTION
Technical Problem
In the case of patterning light-emitting layers etc. by a vacuum
deposition method in a conventional mass production process, the
mask size increases as the substrate size increases. Accordingly, a
gap tends to be produced between the substrate and the mask due to
bending or extension of the mask due to its own weight. This makes
it difficult to perform accurate patterning, and thus to implement
higher definition due to displacement of the deposition position or
color mixture.
As the substrate size increases, the size of the mask, a frame
holding the mask, etc. becomes enormous, and the weight thereof
increases accordingly. Accordingly, it is difficult to handle them,
which may adversely affect productivity and safety. Associated
apparatuses are similarly increased in size and become complicated,
whereby it is difficult to design the devices, and installation
cost become very high.
Accordingly, it is difficult to apply the conventional vacuum
deposition method to the large substrates, and a method that allows
patterning to be performed on large substrates of more than 60
inches by mass production has not been implemented.
The inventor has proposed a deposition method that can be applied
to such large substrates (herein referred to as the "new deposition
method") (Japanese Patent Application No. 2009-213570).
Specifically, a mask unit is used which is formed by integrating a
deposition source and a shadow mask having a smaller area than a
substrate. With the shadow mask and the substrate being held with a
constant gap therebetween, deposition is performed while relatively
scanning the mask unit with respect to the substrate. This avoids
the above problems associated with the increased substrate size,
and allows patterning to be performed on a large substrate by
deposition in a mass production process.
In the new deposition method, however, a patterned thin film has a
non-uniform thickness in some cases.
FIG. 1 is a schematic view showing a deposition process in the new
deposition method. In the figure, the reference character "101"
represents a substrate, "102" represents a deposition mask, "102a"
represents an opening, "103" represents a deposition source, and
"103a" represents an emission port through which deposition
particles are emitted, and "110" represents a thin film such as a
light-emitting layer formed on the substrate. The deposition mask
102 and the deposition source 103 are used as a unit, and are held
in a fixed relative positional relation therebetween. An arrow
represents a relative scanning direction of the deposition mask 102
etc. with respect to the substrate 101.
In the new deposition method, deposition is performed with a
constant gap between the deposition mask 102 and the substrate 101.
Accordingly, as shown in FIG. 2, a phenomenon was observed in which
the thin film 110 was thinner at both ends 110b, 110b than in a
central portion 110a in a direction (a lateral direction of the
thin film 110) perpendicular to the scanning direction. This
phenomenon seemed to occur mainly for the following two
reasons.
(Influence of Deposition Angle)
As shown in FIG. 3, the angle (the deposition angle) at which the
deposition particles can be deposited varies between a central
portion and both ends of a deposition region 101a of the substrate
101, which faces the opening 102a of the deposition mask 102. That
is, since the deposition mask 102 is accurately positioned parallel
to the substrate 101, the deposition angle .theta.1 at which the
deposition particles can be directed to the central portion through
the opening 102a is always larger than the deposition angle
.theta.2 at which the deposition particles can be directed to each
end through the opening 102a. In other words, the width of the
opening 102a though which the deposition particles can pass is
substantially narrower at the ends than in the central portion. As
a result, the deposition particles are less likely to be deposited
on both ends of the deposition region 101a than on the central
portion thereof, whereby the thin film 110 has a difference in
thickness.
(Influence of Deposition Distribution)
The thickness of the thin film 110 can be influenced by
distribution of the deposition particles. For example, measured
deposition distribution is usually as shown in FIG. 4B on a plane
perpendicular to an emission direction (shown by a deposition
centerline L1) of the deposition source 103 as shown in FIG. 4A. In
FIG. 4B, the abscissa represents a spread angle .theta.3 from the
deposition centerline L1, and the ordinate represents a deposition
amount.
The deposition amount is the largest at a position (the spread
angle .theta.3=0.degree.) immediately above the emission port 103a,
and decreases as the distance from this position increases (as the
spread angle .theta.3 increases). Accordingly, if, e.g., the
deposition region 101a is placed so that the central portion
thereof is located immediately above the emission port 103a, the
deposition particles in the distribution center (shown by "S1") are
deposited on the central portion of the deposition region 101a, and
the deposition particles on the right or left side of the
distribution center (shown by "S2") in the figure are deposited on
each end of the deposition range 101a. As a result, the deposition
amount is smaller at both ends of the deposition region 101a than
in the central portion thereof, whereby the thin film 110 has a
difference in thickness.
The thin film having a difference in thickness has the following
problems. For example, if the thickness of an organic film in a
pixel is a predetermined value or more (e.g., 2% or more of an
average thickness), not only the difference in luminance is
visually recognized, but also the luminance decreases in the thin
part of the film due to an increased amount of current caused by a
strong electric field. Moreover, concentration of the electric
field on the thin part of the organic film may cause a
short-circuit between electrodes, which may result in a defective
pixel. Accordingly, it is preferable to make the film thickness as
uniform as possible in order to improve image display performance,
long-term product reliability, etc.
The difference in thickness of the thin film can be eliminated by,
e.g., using the method of Patent Document 2. However, this method
can decrease the amount of reduction in film thickness in a portion
(corresponding to the central portion of the pixel region) between
two adjoining openings, but cannot decrease the amount of reduction
in film thickness at the ends.
Moreover, as described above, the deposition amount is
substantially smaller at the ends of the deposition region than in
the central portion thereof. Accordingly, the difference in film
thickness is not completely eliminated by merely using such
conditions that the deposition amounts of the two ends overlap each
other. In particular, the difference in film thickness in the
central portion of the deposition region is more disadvantageous
than the difference in thickness at the ends of the deposition
region, because the difference in film thickness in the central
portion of the deposition region greatly affects image quality
etc.
Moreover, the difference in thickness decreases as the size of the
thin film decreases. Accordingly, precise setting is required to
substantially eliminate the difference in thickness, but the
conditions used in the above method are not sufficient.
It is an object of the present invention to provide a deposition
mask etc. capable of further improving image display performance,
long-term product reliability, etc. by increasing uniformity of the
film thickness.
Solution to the Problem
In order to achieve the above object, the present invention was
developed in terms of the shape and positioning of a deposition
mask.
For example, a deposition mask of the present invention is used to
form a thin film in a prescribed pattern on a substrate by
deposition. The deposition mask includes: a plate-like mask body;
and a plurality of openings arranged in line in the mask body. The
plurality of openings include an improved opening in which an
opening amount in a longitudinal direction perpendicular to a
lateral direction varies depending on a position in the lateral
direction, and the lateral direction is a direction parallel to a
direction in which the plurality of openings are arranged. The
improved opening is formed so that the opening amount at an end in
the lateral direction is larger than that in a central portion in
the lateral direction.
According to this deposition mask, the improved opening is formed
so that the opening amount at the end in the lateral direction is
larger than that in the central portion in the lateral direction.
Accordingly, deposition time at the end can be increased by
mounting the deposition mask on a deposition apparatus so that the
longitudinal direction is parallel to a scanning direction.
The increased deposition time can compensate for reduction in
thickness at both ends of the thin film, whereby uniformity of the
thickness of the thin film can be improved. As a result, a reliable
organic EL display having high display quality can be
implemented.
Specifically, the improved opening may have a protruding opening
portion in at least one end portion in the longitudinal direction,
and the protruding opening portion may open in the end in the
lateral direction so as to protrude with respect to the central
portion in the lateral direction.
More specifically, the protruding opening portion is preferably
formed so that its opening amount gradually increases as a distance
from the central portion in the lateral direction toward the end in
the lateral direction increases.
Thus, the thickness of the thin film can be made uniform in a
balanced manner from the central portion to the end in the lateral
direction.
The protruding opening portion may be divided into a plurality of
partial opening portions.
This can increase the strength of the deposition mask, and
facilitates formation thereof.
For a deposition process, a deposition apparatus may be used which
includes: such a deposition mask; a deposition source that emits
deposition particles forming the thin film; a mask unit that
includes the deposition mask and the deposition source, and
maintains a fixed relative positional relation between the
deposition mask and the deposition source; a substrate support
apparatus that supports the substrate; and a moving apparatus that
relatively moves at least one of the mask unit and the substrate
along a predetermined scanning direction with a constant gap being
provided between the substrate and the deposition mask, wherein the
deposition mask is placed so that the longitudinal direction is
parallel to the scanning direction.
This allows deposition to be performed even in, e.g., large-sized
organic EL displays. Accordingly, mass production of the
large-sized organic EL displays having excellent image display
performance, high long-term product reliability, etc. can be
implemented.
As a specific example of a deposition method, a deposition method
for forming the thin film in a stripe pattern on the substrate by
using this deposition apparatus includes: an aligning step of, with
the substrate being supported by the substrate support apparatus
and with the gap being provided between the substrate and the
deposition mask, aligning the mask unit and the substrate so that
the mask unit faces the substrate; and a deposition step of forming
the thin film by sequentially depositing the deposition particles
while relatively moving at least one of the mask unit and the
substrate along the predetermined scanning direction by the moving
apparatus.
This deposition method allows the large-sized organic EL displays
having excellent image display performance, high long-term product
reliability, etc. to be manufactured by merely performing a
predetermined operation. Accordingly, this deposition method is
preferable for a mass production process.
In particular, in the case where a substrate for an organic EL
display in which a plurality of pixels each having a light-emitting
region configured to emit light are arranged in a grid pattern is
used as the substrate, the plurality of openings are preferably
placed so as to face a plurality of film formation pixels that are
included in the plurality of pixels, and the deposition mask is
positioned so that each of the light-emitting regions of the film
formation pixels is located inside the improved opening in the
lateral direction with a gap therebetween, as viewed from a
direction perpendicular to the substrate.
Since each of the light-emitting regions of the film formation
pixels is located inside the improved opening with the gap
therebetween, defective formation of the thin film due to a
difference in dimensions between the deposition mask and the
substrate and misalignment therebetween can be reduced, whereby
productivity in a mass production process can be improved.
It is preferable that a first relational expression
(Lw/L.gtoreq.T/Tw) be satisfied, where a centerline passes through
a center in the lateral direction of the improved opening and
extends in the longitudinal direction, "Lw" represents the opening
amount of the improved opening including the protruding opening
portion, at a predetermined distance W from the centerline toward
the end in the lateral direction, and if the improved opening has
no protruding opening portion, "Tw" represents a thickness of the
thin film at the predetermined distance, "L" represents the opening
amount in the central portion in the lateral direction, and "T"
represents a thickness in the central portion in the lateral
direction of the thin film (a unit of "T," "L," "Tw," and "Lw" is
millimeter).
This can easily increase the uniformity of the thin film, whereby
the large-sized organic EL displays having excellent image display
performance, high long-term product reliability, etc. can be easily
implemented.
A deposition apparatus may be configured as follows.
That is, a deposition apparatus that is used to form a thin film in
a prescribed pattern on a substrate by deposition includes: a
deposition mask having a plurality of openings arranged in line; a
deposition source that emits deposition particles forming the thin
film toward the substrate; a mask unit that includes the deposition
mask and the deposition source, and maintains a fixed relative
positional relation between the deposition mask and the deposition
source; a substrate support apparatus that supports the substrate;
and a moving apparatus that relatively moves at least one of the
mask unit and the substrate along a predetermined scanning
direction with a constant gap H being provided between the
substrate and the deposition mask.
The deposition mask is placed so that a lateral direction in which
the plurality of openings are arranged is perpendicular to the
scanning direction. The plurality of openings include a second
improved opening that is formed by a plurality of element openings
separated from each other in the lateral direction. The plurality
of element openings in the second improved opening adjoin each
other with a constant gap S therebetween in the lateral
direction.
A second relational expression (S<H.times.tan .theta.,
.theta.=.alpha. when .alpha..ltoreq..beta., and .theta.=.beta. when
.alpha.>.beta.) is satisfied, where ".alpha." represents a
spread angle at which the deposition particles spread with respect
to an emission direction substantially perpendicular to the
substrate, and ".beta." represents a largest angle at which the
deposition particles can pass through the element opening (a unit
of "S" and "H" is micrometer, and a unit of ".alpha." and ".beta."
is degree), as viewed from the scanning direction.
This configuration can increase uniformity of the film thickness in
the central portion even if, e.g., the width of the thin film is
increased. Moreover, as described below in detail, since the width
of undesirable deposition is reduced, the influence of the end in
the lateral direction of the thin film can be reduced, whereby the
uniformity of the film thickness can be increased accordingly.
A deposition method similar to that used in the above deposition
apparatus can be used in this deposition apparatus.
In particular, in the case where a substrate for an organic EL
display in which a plurality of pixels each having a light-emitting
region configured to emit light are arranged in a grid pattern is
used as the substrate, the deposition mask is preferably positioned
in a manner similar to that of the above deposition apparatus.
Advantages of the Invention
As described above, the deposition mask etc. of the present
invention can increase uniformity of the film thickness, and can
further improve image display performance, long-term product
reliability, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing an example of a deposition
process in a new deposition method.
FIG. 2 is an enlarged schematic diagram of a portion shown by a
two-dot chain line in FIG. 1.
FIG. 3 is a diagram illustrating the influence of a deposition
angle.
FIGS. 4A-4B are diagrams illustrating the influence of deposition
distribution, where FIG. 4A is a schematic diagram showing a
deposition state, and FIG. 4B is a schematic diagram showing
deposition distribution.
FIG. 5 is a schematic cross-sectional view showing an organic EL
display in a first embodiment.
FIG. 6 is a schematic plan view showing a main part of a
substrate.
FIG. 7 is a schematic diagram showing a cross section taken along
line I-I in FIG. 6.
FIG. 8 is a flowchart showing a basic manufacturing process of the
organic EL display.
FIG. 9 is a schematic plan view showing a main part of a deposition
apparatus.
FIG. 10 is a schematic diagram showing a cross section taken along
line II-II in FIG. 9.
FIG. 11 is a schematic diagram showing a main part of a
modification of the deposition apparatus.
FIG. 12 is a flowchart showing a deposition process of a
light-emitting layer.
FIG. 13 is a schematic diagram showing a deposition mask before
improvement.
FIG. 14 is a schematic diagram showing an improved deposition mask
of the first embodiment.
FIGS. 15A-15B are diagrams illustrating a method for setting the
amount by which a protruding opening portion protrudes, where FIG.
15A is a schematic plan view of an improved opening, and FIG. 15B
is a schematic cross-sectional view of an element film.
FIGS. 16A-16E are schematic diagrams showing modifications of the
deposition mask.
FIG. 17 is a schematic plan view showing the positional relation
between the deposition mask and a pixel.
FIG. 18 is a schematic diagram showing a deposition mask in a
second embodiment.
FIG. 19 is a schematic diagram schematically showing a
cross-sectional shape of an element film in the second
embodiment.
FIGS. 20A-20B are diagrams illustrating a second relational
expression, where FIG. 20A shows a deposition source as viewed from
a scanning direction, and FIG. 20B shows the deposition mask and a
substrate as viewed from the scanning direction.
FIG. 21 is a diagram illustrating the width of undesirable
deposition.
FIG. 22 is a diagram illustrating the width of undesirable
deposition.
FIG. 23 is a schematic plan view showing the positional relation
between the deposition mask and a pixel in the second
embodiment.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will be described in detail
below based on the accompanying drawings. The following description
is essentially by way of example only, and is not intended to limit
the present invention, its applications, or its uses.
[First Embodiment]
(Organic EL Display)
The present embodiment is described with respect to an example in
which the present invention is applied to manufacture of organic EL
displays. An organic EL display of the present embodiment is an
active matrix display that implements full color image display by
controlling light emission of a plurality of pixels (sub-pixels) of
red, green, and blue (also collectively referred to as "RGB").
As shown in FIG. 5, an organic EL display 1 of the present
embodiment is formed by a substrate 10, a thin film-like organic EL
element 20, a sealing plate 30, etc. The substrate 10 and the
sealing plate 30 have a shape of a rectangular plate, and the
organic EL element 20 is inserted therebetween and is enclosed and
hermetically sealed by a sealing member 40 such as an adhesive. A
central portion of the surface of the substrate 10 serves as a
display region 11 that provides image display, and the organic EL
element 20 is placed in the display region 11.
As shown in FIGS. 6 and 7, thin film transistors (TFTs) 12,
interconnects 13, an interlayer film 14, etc. are provided in the
display region 11 of the substrate 10.
A glass plate etc. is used as the substrate 10. The substrate 10 is
preferably transparent because the organic EL display 1 of the
present embodiment is of a bottom emission type in which emitted
light is output from the side of the substrate 10. However, the
substrate 10 need not necessarily be transparent if the organic EL
display 1 is of a top emission type. The interconnects 13 are
patterned on the substrate 10, and are comprised of a plurality of
gate lines extending parallel to each other, a plurality of signal
lines crossing the gate lines and extending parallel to each other.
RGB sub-pixels 2R, 2G, 2B are arranged in a plurality of regions
each surrounded by the interconnects 13 such as the gate lines and
forming a grid pattern. The TFTs 12 that control light emission are
respectively provided in the sub-pixels 2R, 2G, 2B.
The RGB sub-pixels 2R, 2G, 2B are arranged so that the sub-pixels
of the same color are arranged in line in a row direction and are
arranged in a repeated pattern of RGB in a column direction. Every
three sub-pixels 2R, 2G, 2B of RGB that are successively arranged
in the column direction form one pixel. As described in detail
below, light-emitting layers 25R, 25G, 25B of the sub-pixels 2R,
2G, 2B are respectively formed by thin films 3 that are formed for
each color so as to have a stripe pattern.
The interlayer film 14 is an insulating thin film of an acrylic
resin etc., which functions also as a planarizing film. The
interlayer film 14 is stacked over the entire display region 11 so
as to cover the TFTs 12 etc. If the organic EL display 1 is of a
bottom emission type, the interlayer film 14 is preferably
transparent.
The organic EL element 20 is formed by first electrodes 21
(anodes), an organic EL layer 22, a second electrode 23 (a
cathode), etc. The first electrodes 21 are comprised of indium tin
oxide (ITO) etc. An ITO film etc. is stacked on the interlayer film
14, and is patterned into the plurality of first electrodes 21 in a
grid pattern corresponding to the sub-pixels 2. The first
electrodes 21 are respectively connected to the TFTs 12 via contact
holes 14a. An insulating edge cover 15 is stacked on the first
electrodes 21. The edge cover 15 has light-emitting regions 16R,
16G, 16B formed as rectangular openings so as to correspond to the
sub-pixels 2, respectively. A large part of the first electrode 21
is exposed from the light-emitting region 16R, 16G, 16B, and the
ends of the first electrode 21 are covered by the edge cover 15.
Light emission of each pixel is output through these light-emitting
regions 16R, 16G, 16B.
The organic EL layer 22 is provided between the first electrodes 21
and the second electrode 23. In the organic EL layer 22 of the
present embodiment, a hole transport layer 24, light-emitting
layers 25R, 25G, 25B, an electron transport layer 26, and an
electron injection layer 27 are sequentially stacked from the side
of the first electrodes 21. The hole transport layer 24 of the
present embodiment also functions as a hole injection layer. The
configuration of the organic EL layer 22 shown in the present
embodiment is merely an example and is not limited to this, and the
organic EL layer 22 may be formed by combining the layers as
necessary. For example, a hole injection layer may be provided
separately from the hole transport layer 24, and a blocking layer
may further be provided. The organic EL layer 22 need only include
at least the light-emitting layers 25R, 25G, 25B. Known materials
can be used as the materials of the hole transport layer 24, the
light-emitting layers 25R, 25G, 25B, etc.
The hole transport layer 24, the electron transport layer 26, and
the electron injection layer 27 are stacked over the entire display
region 11. As described above, the light-emitting layers 25R, 25G,
25B have a stripe pattern corresponding to the sub-pixels 2 of each
color. The second electrode 23 is stacked over the entire display
region 11 so as to cover the organic EL layer 22.
(Basic Manufacturing Method of Organic EL Display 1)
A basic manufacturing method of the above organic EL display 1 will
be described with reference to FIG. 8. FIG. 8 shows the step of
forming the hole transport layer 24 etc. in the organic EL element
20 among the steps of the manufacturing method of the organic EL
display 1.
First, the substrate 10 having formed thereon the TFTs 12, the
first electrodes 21, etc. is prepared (also referred to as the "TFT
substrate 10"). For example, a 500.times.400 mm rectangular glass
plate having a thickness of about 1 mm can be used as a base of the
TFT substrate 10. In this case, the interlayer film 14 can be
formed with a thickness of about 2 .mu.m, the first electrodes 21
can be formed with a thickness of about 100 nm, and the edge cover
15 can be formed with a thickness of about 1 .mu.m. Since the TFT
substrate 10 can be formed by a known method, description thereof
is omitted.
The hole transport layer 24 is formed over the prepared TFT
substrate 10 so as to cover the TFTs 12 etc. (step S1).
Specifically, the material of the hole transport layer 24 is
deposited over the entire display region 11. For example, a mask
for the entire region, which has an opening of the same size as the
display region 11, is bonded to the TFT substrate 10 so as to be in
close contact therewith. The material of the hole transport layer
24 is deposited while rotating the TFT substrate 10 having thereon
the mask for the entire region. For example, the hole transport
layer 24 can be formed with a thickness of about 30 nm by using
.alpha.-NPD. A conventional deposition apparatus can be used for
this deposition process.
Next, the light-emitting layers 25R, 25G, 25B are stacked on the
hole transport layer 24 (step S2). The light-emitting layers 25R,
25G, 25B of RGB are separately deposited color by color (separate
deposition). The light-emitting layers 25R, 25G, 25B are typically
deposited by co-deposition using a host material and a dopant
material. Materials selected from known materials can be used as
the materials of the light-emitting layers 25R, 25G, 25B, such as
the host material and the dopant material. The light-emitting
layers 25R, 25G, 25B can be formed with a thickness in the range
of, e.g., 10-100 nm. In the present embodiment, the new deposition
method and the deposition apparatus are used in this step, and will
be described in detail later.
Then, the electron transport layer 26 is stacked on the
light-emitting layers 25R, 25G, 25B (step S3). Specifically, the
material of the electron transport layer 26 is deposited over the
entire display region 11 by the same method as that used for the
hole transport layer 24. Moreover, the electron injection layer 27
is stacked on the electron transport layer 26 (step S4). The
electron injection layer 27 is also formed by the same method as
that used for the hole transport layer 24, by depositing the
material of the electron injection layer 27 over the entire display
region 11.
Materials selected from known materials can be used as the
materials of the electron transport layer 26 and the electron
injection layer 27. Both the electron transport layer 26 and the
electron injection layer 27 may be integrally formed by using the
same material. Each of the electron transport layer 26 and the
electron injection layer 27 may be formed with a thickness in the
range of, e.g., 10-100 nm For example, the electron transport layer
26 may be formed with a thickness of 30 nm by using Alq, and the
electron injection layer 27 may be formed with a thickness of 1 nm
by using LiF.
Then, the second electrode 23 is stacked on the electron injection
layer 27 (step S5). The second electrode 23 is also formed by the
same method as that used for the hole transport layer 24, by
depositing the material of the second electrode 23 over the entire
display region 11. A material selected from known materials can be
used as the material of the second electrode 23. For example, the
second electrode 23 may be formed with a thickness of 50 nm by
using aluminum (Al).
Lastly, the TFT substrate 10 having the organic EL element 20 thus
formed thereon is bonded to the sealing plate 30 to hermetically
seal the organic EL element 20. Thus, a main portion of the organic
EL display 1 is completed.
(Separate Deposition)
The step of forming the light-emitting layers 25R, 25G, 25B by
separate deposition (step S2) will be described below. Since the
new deposition method and the deposition apparatus described above
are used in this step, the basic configuration thereof will first
be described.
(Deposition Apparatus)
FIGS. 9 and 10 show a deposition apparatus 50 of the present
embodiment. As shown in these figures, the deposition apparatus 50
includes a vacuum chamber 51, a substrate support apparatus 52, a
deposition source 53, a shadow mask 60 (a deposition mask), a mask
unit 55, a moving apparatus 56, etc. The deposition apparatus 50 of
the present embodiment is of a type in which deposition particles
are emitted upward.
The vacuum chamber 51 is a box-shaped airtight container that can
be opened and closed. The inside of the vacuum chamber 51 can be
decompressed and held in a predetermined low pressure state by a
decompression apparatus located outside the figure.
The substrate support apparatus 52 has a function to horizontally
support the substrate 10 to be processed (also referred to as the
"target substrate 10"), so that the row direction (the direction in
which the sub-pixels 2R, 2G, 2B of each color are arranged in line)
extends in the direction (the scanning direction) shown by an arrow
in FIG. 9. For example, if the substrate support apparatus 52 is
provided with an electrostatic chuck, the target substrate 10 can
be held by the electrostatic chuck, and thus can be supported
without being bent by its own weight.
The substrate support apparatus 52 is capable of moving
horizontally, and the horizontal movement of the substrate support
apparatus 52 in the scanning direction is automatically controlled
by the moving apparatus 56. For convenience, the scanning direction
is also referred to as the "X-axis direction," and the direction
perpendicular to the scanning direction is also referred to as the
"Y-axis direction." The X-axis and Y-axis directions are shown as
appropriate in the figures.
The shadow mask 60 is horizontally placed below the target
substrate 10 supported by the substrate support apparatus 52, with
a constant gap H between the shadow mask 60 and the target
substrate 10. The vertical distance (the shortest distance) of the
gap H is preferably in the range of 50 .mu.m to 1 mm If the
vertical distance of the gap H is less than 50 .mu.m, the target
substrate 10 may contact the shadow mask 60. If the vertical
distance of the gap H exceeds 1 mm, the deposition range may be
excessively increased due to the deposition angle of the deposition
particles, which may cause color mixture or reduction in patterning
accuracy.
The shadow mask 60 has a rectangular plate-like mask body 61
comprised of a metal, and a plurality of openings 62, 62, . . .
formed in a stripe pattern so as to be arranged in line in the
direction along the longer side of the mask body 61 and to extend
along the shorter side of the mask body 61 (only some of the
openings are shown in the figures). For example, the plurality of
openings 62, 62, . . . are formed so as to correspond to the rows
of the sub-pixels 2R, 2G, 2B of each color of RGB. The dimension of
the longer side of the mask body 61 is larger than the dimension in
the Y-axis direction of the display region 11 of the target
substrate 10 facing the mask body 61. The dimension of the shorter
side of the mask body 61 is smaller than the dimension in the
X-axis direction of the display region 11 of the target substrate
10 facing the mask body 61. The plurality of openings 62, 62, . . .
are provided in the range corresponding to the display region 11 in
the Y axial direction (an effective region).
A second marker 63 for alignment with a first marker 17 provided on
the target substrate 10 is provided on both sides of the effective
region. The first marker 17 and the second marker 63 are detected
by a sensor 57 provided in the deposition apparatus 50, and the
target substrate 10 and the shadow mask 60 are accurately
positioned in the horizontal direction based on the detection value
(these markers and the sensor are also referred to as the
"positioning mechanism"). The shadow mask 60 is detachably mounted
in the mask unit 55 so that the shorter side of the shadow mask 60
is parallel to the scanning direction. The shadow mask 60 will be
described in detail later.
The mask unit 55 is provided with a holder 55a, a tension retaining
apparatus 58, the deposition source 53, etc. The shadow mask 60
mounted in the mask unit 55 is horizontally supported by the
tension retaining apparatus 58, and is held in a fixed relative
positional relation with the deposition source 53 by the holder
55a.
The deposition source 53 is provided so as to extend along the
Y-axis direction. The deposition source 53 is placed below the
shadow mask 60 so as to face the target substrate 10 with the
shadow mask 60 interposed therebetween. A plurality of emission
ports 53a, 53a, . . . , from which the deposition particles are
emitted toward the target substrate 10, are provided so as to be
arranged in line in the Y-axis direction (only some of the emission
ports are shown in the figures). In the present embodiment, these
emission ports 53a, 53a, . . . are arranged at the positions
corresponding to the openings 62 of the shadow mask 60,
respectively, and each emission port 53a is located in the center
(the center in both X-axis and Y-axis directions) of a
corresponding one of the openings 62 as viewed in plan. The
deposition apparatus 50 is provided with a shutter (not shown) that
opens and closes the space between the deposition source 53 and the
shadow masks 60. By controlling opening and closing of the shutter,
the deposition apparatus 50 is automatically controlled so that
deposition can be performed at appropriate timing.
The deposition apparatus 50 may have various configurations other
than the above configuration of the deposition apparatus 50. For
example, the deposition apparatus 50 may be configured so that the
mask unit 55 is moved, rather than being configured so that the
substrate 10 is moved. The number of emission ports 53a and the
arrangement thereof can be adjusted as appropriate.
As shown in FIG. 11, the positions of the mask unit 55 and the
substrate support apparatus 52 may be reversed so that the
deposition particles are emitted downward. Since the configuration
and function of each member etc. are similar to those of the
deposition apparatus 50 of the present embodiment, the same
reference characters are used, and description thereof is omitted.
The mask unit 55 can be easily moved in this case. This
configuration is also advantageous in that the target substrate 10
can be easily supported.
(Deposition Method)
FIG. 12 shows main steps of the deposition method. For example, the
shadow mask 60 for the red (R) light-emitting layer 25R is mounted
in the mask unit 55, and the shadow mask 60 is horizontally
supported by the tension retaining apparatus 58 (step S11). At this
time, the shadow mask 60 and the deposition source 53 are held in a
fixed predetermined positional relation. A material for the red (R)
light-emitting layer 25R has been placed in the deposition source
53. Next, the target substrate 10 is attached to and supported by
the substrate support apparatus 52 so that the row direction of the
target substrate 10 is parallel to the scanning direction (step
S12). Then, the target substrate 10 and the shadow mask 60 are
placed so as to face each other, and are aligned in the vertical
direction so that the predetermined gap H is provided between the
target substrate 10 and the shadow mask 60 (the alignment step,
step S13).
After the target substrate 10 etc. is thus placed in the deposition
apparatus 50, the deposition apparatus 50 is operated to perform
deposition on the entire display region 11 of the target substrate
10 while scanning the target substrate 10 (the deposition step,
step S14). In this deposition step, the target substrate 10 moves
in the scanning direction at a constant scanning speed. The target
substrate 10 has been accurately positioned in the horizontal
direction with respect to the shadow mask 60 by the positioning
mechanism. During the deposition step, the deposition particles are
emitted from the deposition source 53, and are sequentially
deposited on the target substrate 10 through the openings 62 of the
shadow mask 60, whereby a thin film 3 is formed. The thickness of
the thin film 3 can be controlled by, e.g., adjusting the scanning
speed and the number of scanning times. After the deposition step,
the thin film 3 (the red light-emitting layer 25R) having a stripe
pattern is formed in the regions of the red (R) sub-pixels 2R, 2R,
. . . of the target substrate 10.
After the red (R) light-emitting layer 25R is formed, the green (G)
and blue (B) light-emitting layers 25G, 25B can be formed by the
same deposition method by changing the shadow mask 60 and the
materials of the deposition source 53. Since the sub-pixels 2R, 2G,
2B of each color of RGB are arranged at the same pitch, the same
shadow mask 60 can be used for the sub-pixels 2R, 2G, 2B of the
three colors by, e.g., shifting (moving) the shadow mask 60 in the
Y-axis direction by a predetermined pitch.
(Deposition Mask)
As described above, in the new deposition method, the thin film 3
formed in a stripe pattern had a non-uniform thickness in some
cases. That is, since the deposition amount was smaller at the ends
(the ends in the Y-axis direction) of the opening 62 of the shadow
mask 60, an individual film of the thin film 3 having a stripe
pattern, specifically a film extending in a band shape (linearly)
(also referred to as the "element film 3"), had a smaller thickness
at its lateral ends.
In this case, a shadow mask 600 having rectangular strip-shaped
openings 62 as shown in FIG. 13 was used as the shadow mask 60.
However, a new shadow mask 60 (also referred to as the "improved
mask 601") was produced in order to increase uniformity of the film
thickness. The common members etc. of the masks are denoted by the
same reference characters.
FIG. 14 shows the improved mask 601. The improved mask 601 has a
rectangular plate-like mask body 61, and a plurality of
strip-shaped (slit-like) openings (improved openings) 62A, 62A, . .
. arranged in line along the longer side of the mask body 61 and
formed so as to extend in the shorter side of the mask body 61.
Each improved opening 62A is formed so that its opening amount
(length) in the longitudinal direction (the direction perpendicular
to the lateral direction; the X-axis direction when the improved
mask 601 is mounted in the deposition apparatus 50) varies
depending on the position in the lateral direction (the direction
in which the openings 62A are arranged; the Y-axis direction when
the improved mask 601 is mounted in the deposition apparatus 50).
Specifically, each improved opening 62A is formed so as to have a
larger opening amount at the ends in the lateral direction than in
the central portion in the lateral direction.
More specifically, as shown also in FIG. 15A, the improved opening
62A is shaped so that both end portions 62a, 62a in the
longitudinal direction protrude in an M shape. That is, in the both
end portions 62a, 62a in the longitudinal direction, the improved
opening 62A has protruding opening portions 64, 64 at each end in
the lateral direction, and the protruding opening portions 64, 64
are formed so as to protrude with respect to the central portion in
the lateral direction. The protruding opening portions 64, 64 are
formed so that the opening amount gradually increases as the
distance from the central portion in the lateral direction toward
the end in the lateral direction increases. Each end face 62b of
the protruding opening portions 64 is formed to have a parabolic
shape.
According to the improved mask 601 shaped as described above, each
improved opening 62A has a larger opening amount at both ends in
the Y-axis direction than in the central portion in the Y-axis
direction. Accordingly, when performing deposition while scanning,
the deposition time is longer at both ends than in the central
portion. If the deposition time is increased, the deposition amount
is increased accordingly, whereby the reduction in thickness at the
lateral ends of the element film 3 can be compensated for.
Referring to FIGS. 15A-15B, the amount by which the protruding
opening portion 64 protrudes can be determined as follows. That is,
as shown in FIG. 15A, "L2" represents a centerline that passes
through the center in the lateral direction of the improved opening
62A and extends in the longitudinal direction, and "Lw" represents
the opening amount including the protruding opening portion 64, at
a predetermined distance W from the centerline L2 toward the end in
the lateral direction. If the improved opening 62A has no
protruding opening portion 64, and is formed only by a rectangular
opening (an imaginary opening 62c) as shown by an imaginary line in
FIG. 15A, "Tw" represents the thickness of the element film (an
imaginary element film 3a) at the predetermined distance, as shown
by an imaginary line in FIG. 15B. "L" represents the opening amount
in the central portion in the lateral direction of the imaginary
opening 62c (the improved opening 62A), and "T" represents the
thickness in the central portion in the lateral direction of the
imaginary element film 3a.
In this case, the protruding opening portion 64 is formed so as to
satisfy a first relational expression (Lw/L.gtoreq.T/Tw). The unit
of "T," "L," "Tw," and "Lw" is millimeter (mm).
Since a constant scanning speed and a constant positional relation
of the target substrate 10 etc. can be accurately maintained during
deposition, determining the opening amount based on the first
relational expression allows the film thickness at the lateral ends
to be accurately adjusted. Providing the protruding opening portion
64 may increase the thickness in the central portion of the element
film 3. In this case, the amount Lw can be finely adjusted in a
range that is larger than the value obtained by the equation of the
first relational expression.
(Modification of Deposition Mask)
As shown in FIGS. 16A-16E, the improved mask 601 may be formed in a
different shape from the shape described above. For example, in an
improved mask 601a shown in FIG. 16A, the protruding opening
portions 64 are provided only in one end portion 62a in the
longitudinal direction of the improved opening 62A (the other end
portion 62a is rectangular). In an improved mask 601b of FIG. 16B,
the end faces 62b of the protruding opening portions 64 are formed
linearly. Namely, in one or both end portions 62a in the
longitudinal direction of the improved opening 62A, the opening
amount at both ends in the lateral direction need only be larger by
a predetermined amount than that in the central portion in the
lateral direction, and the one or both end portions 62a may have
any shape.
For example, as shown in FIGS. 16C-16E, each protruding opening
portion 64 of the improved mask 601 may be divided into a plurality
of partial opening portions 65, 65, . . . Combining the rectangular
partial opening portions 65 to form the protruding opening portion
64 increases the strength of the mask, and facilitates formation of
the mask.
(Positional Relation between Deposition Mask and Pixel)
It is preferable that the improved opening 62A of the improved mask
601 have a predetermined positional relation with the sub-pixels
2R, 2G, 2B of the target substrate 10. FIG. 17 shows a state (a
state in the deposition process) where, e.g., the target substrate
10 is accurately positioned in the horizontal direction with
respect to the improved mask 601 by the positioning mechanism. In
FIG. 17, the substrate 10 is viewed in the direction perpendicular
to the substrate 10 from the side of the deposition source 53. For
better understanding, the shaded region in the figure shows the
portion except the light-emitting regions 16R, 16G, 16B in the
substrate 10. In this case, the improved openings 62A are placed so
as to face the sub-pixels 2R, 2G, 2B (pixels 2a to be formed,
hereinafter referred to as the "film formation pixels 2a") in which
the element films 3 are formed, respectively. For example, in the
Y-axis direction, two rows of the green (G) and blue (B) sub-pixels
2G, 2B are present between two adjacent columns of the red (R)
sub-pixels 2R, 2R. Accordingly, when forming the red (R)
light-emitting layer 25R, the improved openings 62A are provided
only in the portions facing the columns of the red (R) sub-pixels
2R.
As shown in FIG. 17, the improved mask 601 is positioned so that
each of the light-emitting regions 16R, 16G, 16B of the film
formation pixels 2a is located inside the improved opening 62A with
a gap "g" therebetween.
Specifically, the predetermined amount of gap "g" (a design margin)
is provided between the inner edge of the improved opening 62A,
which extends in the X-axis direction, and the outer edge of the
light-emitting region, which extends in the X-axis direction.
Providing the design margin can reduce defective formation of the
element films 3 due to a difference in dimensions between the
improved mask 601 and the target substrate 10 and misalignment
therebetween, whereby productivity in a mass production process can
be improved.
FIRST EXAMPLE
The light-emitting layers 25R, 25G, 25B were formed by using the
improved mask 601, the deposition apparatus 50, and the new
deposition method described above. The improved mask 601 used in
this example had a size of 200 mm (the X-axis direction).times.600
mm (the Y-axis direction) with a thickness of 550 .mu.m. The gap H
between the target substrate 10 and the improved mask 601 was 200
.mu.m. Each improved opening 62A had a width (the Y-axis direction)
of 110 .mu.m, and had a length (the X-axis direction) of 150 mm in
its central portion and a length of 154.4 mm at the ends. The pitch
of the improved openings 62A in the Y-axis direction was 450 .mu.m.
Each light-emitting region 16R, 16G, 16B of the film formation
pixels 2a had a size of 300 .mu.m (the X-axis direction).times.90
.mu.m (the Y-axis direction), and the pitch of the light-emitting
regions 16R, 16G, 16B was 450 .mu.m in the X-axis direction and 150
.mu.m in the Y-axis direction.
A host material and a dopant material were used as the materials of
the light-emitting layers 25R, 25G, 25B of each color, and the
deposition speeds of these materials were 5.0 nm/s and 0.53 nm/s
for red (R), 5.0 nm/s and 0.67 nm/s for green (G), and 5.0 nm/s and
0.67 nm/s for blue (B). Scanning with one reciprocating motion was
performed once in the deposition process.
As a result, the RGB light-emitting layers 25R, 25G, 25B having a
very uniform thickness were able to be formed.
The improved mask 601 may be used only to form the light-emitting
layer 25R, 25G, 25B of at least one of the three colors. For
example, in the case where non-uniformity of the thickness of the
green (G) light-emitting layer 25G has substantially no influence
on the quality, or the light-emitting region 16G can be formed only
in the central portion where the thickness is relatively uniform,
the shadow mask 60 before improvement can be used for the green (G)
light-emitting layer 25G.
[Second Embodiment]
In the present embodiment, the shadow mask 60 and the mounting
conditions thereof are changed so that, e.g., the uniformity of the
thickness in the central portion of the element film 3 can be
improved even if the width of the element film 3 is increased.
Since the deposition apparatus 50, the deposition method, etc. are
similar to those of the first embodiment, differences will be
described in detail. Similar configurations and members will be
denoted with the same reference characters, and description thereof
will be omitted.
(Deposition Mask)
As shown in FIG. 18, the shadow mask 60 whose openings 62 have a
different shape (a second improved mask 602) is used in the present
embodiment. As shown in the figure, the openings 62 of the second
improved mask 602 are formed by a plurality of element openings 67
separated in the lateral direction (second improved openings
62B).
Each second improved opening 62B of the present embodiment is
formed by two rectangular band-shaped element openings 67, 67
formed by dividing the rectangular band-shaped opening 62 into two
portions, and extending parallel to each other. The two element
openings 67, 67 have the same width and extend through the second
improved mask 602 substantially perpendicularly to the mask
surface. The two element openings 67, 67 adjoin each other with a
constant gap S therebetween in the lateral direction.
Although the number of element openings 67 is two in the present
embodiment, the number of element openings 67 may be three or more.
Increasing the number of element openings 67 can reduce undesirable
deposition as described below, but has disadvantages such as making
formation of the mask difficult. Accordingly, the number of element
openings 67 is preferably 2 to 4.
FIG. 19 schematically shows the cross-sectional shape of the
element film 3 that is formed by using the second improved mask
602. As shown in the figure, deposition particles pass through the
element openings 57 and adhere to the target substrate 10 to form
two element films 3. At this time, adjoining ends of the two
element films 3 overlap each other to form a single element film 3
(also referred to as the "coupled element film 3"). Predetermined
conditions are used for the second improved mask 602 and the
deposition apparatus 50 so that the coupled element film 3
including the overlapping portion has a uniform thickness.
These conditions will be described with reference to FIGS. 20A-20B.
FIG. 20A shows the deposition source 53 as viewed from the scanning
direction, and FIG. 20B shows the second improved mask 602 and the
target substrate 10 as viewed from the scanning direction. In the
figures, the reference character "L3" represents a reference line
indicating a direction substantially perpendicular to the target
substrate 10.
As shown in FIG. 20A, each emission port 53a of the deposition
source 53 is formed so that the emission direction thereof is
aligned with the reference line L3, and the deposition particles
are emitted in a radial fashion from each emission port 53a toward
the target substrate 10. In this example, ".alpha." represents the
largest angle (spread angle) at which the deposition particles
spread with respect to the emission direction.
As shown in FIG. 20B, the angle at which the deposition particles
pass through each element opening 67 is limited by the opening
width of the element opening 67 etc. ".beta." represents the
largest angle at which the deposition particles can pass through
the element opening 67. The gap H between the target substrate 10
and the second improved mask 602 as described above and the
interval S between the two element openings 67, 67 are determined
so as to satisfy a second relational expression (S<H.times.tan
.theta., .theta.=.alpha. when .alpha..ltoreq..beta., and
.theta.=.beta. when .alpha.>.beta.). The unit of "S" and "H" is
micrometer (.mu.m), and the unit of ".alpha." and ".beta." is
degree (.degree.).
In general, the spread angle .alpha. of the deposition particles is
often larger than the angle .beta. of the deposition particles, and
thus the angle at which the deposition particles are deposited on
the target substrate 10 is limited by the angle .beta.. That is,
.theta. is often equal to .beta.. Accordingly, in this case,
adjustment is difficult if the conditions are determined based on
the spread angle .alpha. of the deposition particles, and it is
difficult to obtain a uniform film thickness. In the present
embodiment, since the conditions are determined in consideration of
the angle .beta., accurate adjustment can be made relatively
easily.
Since excessively reducing the value of the interval S increases
the thickness in the central portion, fine adjustment can be made
according to the situation. The angle .beta. of the deposition
particles also varies depending on the thickness of the second
improved mask 602, the interval S, and the cross-sectional shape of
the element opening 67, etc. The element openings 67 of the present
embodiment are formed to extend substantially perpendicularly to
the mask surface. However, for example, the element openings 67 may
be formed to extend obliquely.
Moreover, the second improved mask 602 is advantageous in that the
width of undesirable deposition (the width of the element film 3
that is formed outside the opening 62 of the shadow mask 60) can be
reduced.
As shown in FIG. 21, in the case where, e.g., a wide element film 3
is formed by using the shadow mask 60 before improvement in which
each opening 62 is formed by a single opening, ".theta." in the
second relational expression is equal to ".alpha.," and the width
of undesirable deposition (shown by reference character "B" in the
figure) is equal to "H.times.tan .alpha." due to the large opening
width. On the other hand, as shown in FIG. 22, in the case where
the same element film 3 is formed by using the plurality of element
openings 67, ".theta." in the second relational expression is equal
to ".beta.," and the width B of undesirable deposition is equal to
"H.times.tan .beta." due to the narrow opening width. Since
.alpha.>.beta., the second improved mask 602 in which each
opening 62 is formed by the plurality of element openings 67
provides a narrower width B of undesirable deposition than the
shadow mask 60 before improvement.
If the amount of undesirable deposition is large, the deposited
film may enter an adjoining one of the sub-pixels 2R, 2G, 2B,
causing color mixture or a defective pixel. Accordingly, the pitch
of the sub-pixels 2R, 2G, 2B need be determined in view of the
undesirable deposition. In the present embodiment, since the width
B of undesirable deposition can be reduced, the opening 62 assigned
to each sub-pixel 2R, 2G, 2B can be made to have a relatively large
width. This can reduce the influence of the ends in the lateral
direction of the coupled element film 3, whereby uniformity of the
film thickness in the light-emitting regions 16R, 16G, 16B can be
improved.
Moreover, increasing the width of the opening 62 tends to cause
deformation of the shadow mask 60 such as distortion, due to stress
or thermal expansion. Such deformation of the shadow mask 60
significantly affects deposition accuracy. Since each opening 62 is
formed by the plurality of element openings 67, the second improved
mask 602 is also advantageous in that structural rigidity can be
increased and deformation can be suppressed.
Furthermore, since the target substrate 10 is not integral with the
second improved mask 602, and the target substrate 10 and the
second improved mask 602 can be positioned so as to have the gap H
therebetween, fine adjustment of the second relational expression
can be easily made, resulting in high productivity in a mass
production process.
FIG. 23 shows a diagram corresponding to FIG. 17 in the present
embodiment. As shown in FIG. 23, in the present embodiment as well,
the second improved mask 602 is positioned so that each of the
light-emitting regions 16R, 16G, 16B of the film formation pixels
2a is located inside the second improved opening 62B with a gap "g"
therebetween. Specifically, the predetermined amount of gap "g" (a
design margin) is provided between the outer edge of the element
opening 67 located at the outermost position in the Y-axis
direction in the second improved opening 62B and the outer edge of
the light-emitting region 16R, 16G, 16B.
In the present embodiment, defective formation of the coupled
element film 3 can be reduced. Moreover, reduction in film
thickness at the ends in the lateral direction can be prevented
from affecting the light-emitting regions 16R, 16G, 16B.
SECOND EXAMPLE
The light-emitting layers 25R, 25G, 25B were formed by using the
second improved mask 602, the deposition apparatus 50, and the new
deposition method described above. As in the first example, the
second improved mask 602 used in this example had a size of 200 mm
(the X-axis direction).times.600 mm (the Y-axis direction) with a
thickness of 550 .mu.m. The gap H between the target substrate 10
and the second improved mask 602 was 200 .mu.m. Each of the second
improved openings 62A was formed by two element openings 67, 67.
The element openings 67, 67 had an opening width of 55 .mu.m, and
the interval S between the element openings 67, 67 was 19
.mu.m.
Each of the second improved openings 62B had a length (the X-axis
direction) of 150 mm The pitch of the second improved openings 62B
in the Y-axis direction was 450 .mu.m. Each light-emitting region
16R, 16G, 16B of the film formation pixels 2a had a size of 300
.mu.m (the X-axis direction).times.90 .mu.m (the Y-axis direction),
and the pitch of the light-emitting regions 16R, 16G, 16B was 450
.mu.m in the X-axis direction and 150 .mu.m in the Y-axis
direction. The materials of the light-emitting layers 25R, 25G,
25B, the deposition speed, the deposition method, etc. are the same
as those of the first embodiment.
Regarding the second relational expression, the spread angle
.alpha. of the deposition particles was 20.degree. or more, while
the angle .beta. of the deposition particles was 5.7.degree.
(.theta.=5.7.degree.).
As a result, the RGB light-emitting layers 25R, 25G, 25B having a
very uniform thickness with a narrow width B of undesirable
deposition were able to be formed.
For example, in the shadow mask 60 having a thickness of 550 .mu.m,
if the opening 62 corresponding to each row of the sub-pixels 2R,
2G, 2B is formed by a single opening, and the opening 62 has an
opening width of 110 .mu.m, the opening 62 has a cross-sectional
aspect ratio (a transverse cross-sectional aspect ratio) of 5
(=550/110) in the Y-axis direction. In this example, however, since
each element opening 67 has an opening width of 55 .mu.m, the
transverse cross-sectional aspect ratio of the element opening 67
is 10 (=550/55). Thus, the transverse cross-sectional aspect ratio
is increased.
As the transverse cross-sectional aspect ratio is increased, the
angle .beta. of the deposition particles is reduced, and thus the
width B of undesirable deposition can be reduced. For example, the
width B of undesirable deposition was 40 .mu.m in the case of the
single opening 62, but was able to be reduced to 20 .mu.m in this
example.
Although the opening width is 110 .mu.m in the case of the single
opening 62, a substantial opening width is 129 .mu.m
(=55.times.2+19) in this example, which is larger than that in the
case of the single opening 62. As a result, the ends in the lateral
direction of the second improved opening 62B are located farther
away from the light-emitting regions 16R, 16G, 16B. Accordingly,
even if the film thickness is reduced at the ends in the lateral
direction, the influence of such reduction in film thickness on the
light-emitting regions 16R, 16G, 16B can be reduced.
The interval S between the element openings 67, which is 19 .mu.m,
satisfies the second relational expression. That is, as described
above, since .theta. is 5.7.degree., and the gap H between the
target substrate 10 and the second improved mask 602 is 200 .mu.m,
"H.times.tan .theta." is 20 .mu.m, and the interval S satisfies the
second relational expression.
In this case, according to the expression of Patent Document 2, the
interval between the element openings 67 is 70 .mu.m or more, and
the overlapping portion may have a non-uniform thickness.
As described above, according to the deposition mask etc. of the
present invention, uniformity of the film thickness, which is an
important quality in deposition, can be improved by merely changing
the shape of the openings of the deposition mask and the setting
conditions of the deposition apparatus. Accordingly, image display
performance, long-term product reliability, etc. of organic EL
displays can further be improved without requiring high facility
cost such as adding special processes and devices.
Description of Reference Characters
1 Organic EL Display 2R, 2G, 2B Sub-pixel 3 Thin Film, Element Film
10 Substrate 11 Display Region 16R, 16G, 16B Light-Emitting Region
20 Organic EL Element 21 First Electrode 22 Organic EL Layer 23
Second Electrode 24 Hole Transport Layer 25R, 25G, 25B
Light-Emitting Layer 26 Electron Transport Layer 27 Electronic
Injection Layer 30 Sealing Plate 40 Sealing Member 50 Deposition
Apparatus 51 Vacuum Chamber 52 Substrate Support Apparatus 53
Deposition Source 53a Emission Port 55 Mask Unit 56 Moving
Apparatus 60 Shadow Mask 61 Mask Body 62 Opening 62A Improved
Opening 62B Second Improved Opening 62a End Portion 64 Protruding
Opening Portion 65 Partial Opening Portion 67 Element Opening 601
Improved Mask 602 Second Improved Mask L2 Centerline H Gap S
Interval g Gap
* * * * *